Pneumatic springs, commonly referred to as air springs, have been used for motor vehicles for a number of years to provide cushioning between movable parts of the vehicle, primarily to absorb shock loads impressed on the vehicle axles by the wheels striking an object in the road or falling into a depression. The air spring usually consists of a flexible rubber sleeve or bellows containing a supply of compressed fluid and has one or more pistons located within the flexible resilient sleeve. The piston causes compression and expansion of the fluid within the sleeve as the sleeve compresses and expands as the vehicle experiences the road shocks. The spring sleeve is formed of a flexible elastomeric material which permits the pistons to move axially with respect to the sleeve and within the interior of the sleeve.
The ends of the sleeves are sealingly connected to the piston and/or an opposite end cap if only one piston is used in the particular spring construction. The clamping of the ends of the flexible sleeve onto the piston and/or end member is always one of the important and major assembling steps in the production of air springs. Heretofore, the usual manner of sealing the sleeve against the piston and/or end cap has been by clamping an exteriorly located metal band against the flexible sleeve which crimps and squeezes the rubber material thereof against a sealing surface of the piston or end member. These prior art sealing methods and structures require a permanent deformation of the clamping band and require equipment to supply sufficient pressure to the metal clamping band to permanently deform the metal upon crimping it radially inwardly against the sealing surface of the adjacent air spring member.
It is preferred for certain air spring applications to internally clamp one or both ends of the flexible sleeve outwardly against an inner surface of the end cap and/or piston member to save space and reduce the number of components needed in the air spring assembly. Several known prior art devices having flexible sleeves including air springs use an internal clamping band and are shown in the patents described briefly below.
U.S. Pat. No. 2,115,072 shows the sealing of both ends of the sleeve of an air spring by trapping them in an annular groove of end caps in combination with external annular clamping rings which are bolted to the end caps.
U.S. Pat. No. 2,641,486 shows a usual split ring clamping arrangement. The split ring is compressed by reducing the spacing of the gap between the split ends of the ring afterwhich the ring expands outwardly against a sleeve of material clamping the sleeve internally against an outer supporting structure. However, split rings cannot readily obtain the amount of clamping force required to form a satisfactory seal in an air spring application.
U.S. Pat. No. 3,027,176 shows an air spring having an internal sealing arrangement by use of an annular bead at the ends of the flexible sleeve similar to the sealing bead of a pneumatic tire.
U.S. Pat. No. 3,053,528 shows an air spring in which one end of the flexible sleeve is internally clamped against an outer cylindrical housing by a wedge shaped end cap. The cap is forced into a wedging relationship with the end of the flexible sleeve by the internal fluid pressure of the air spring.
U.S. Pat. No. 3,527,451 shows a shock absorber which is believed to be the closest known prior art to the subject invention. The shock absorber has an internal band which clamps the flexible sleeve against the inner surface of an outer cylindrical housing. It is believed that the internal clamping is achieved either by a wedging action of the internal clamping band against the trapped flexible sleeve end or by a permanent deformation of the internal clamping band in a similar manner as the crimping of a sealing band on the exterior of the flexible sleeve as used in many prior external clamping band arrangements.
Therefore, the need has existed for an improved air spring and method of making the same which contains an internal sealing band for sealingly securing the flexible sleeve against an end cap and/or piston member of the air spring.